The proposed equipment is for upgrading the computational facilities at the University of Washington positron emission tomograph (PET) facility. The equipment will be used to solve a major problem in image reconstruction times (limiting the number of studies that can be performed) and to allow the PET system to acquire all of its image planes at the maximum counting rates the machine is capable of sustaining. The PET facility was established to support a wide variety of investigations. One of the requirements for the facility was the ability to support high dose dynamic studies to allow extraction of time activity curves with small time bins (down to 1 or 2 seconds per image). That requirement resulted in the purchase of a Scanditronix/PETT Electronics SP- 3000 time-of-flight PET system (TOFPET). The system was installed in 1987 with a University of Washington data acquisition/reconstruction computer (developed from 1986 to 1987). The laboratory physics group has made many significant changes in the system to improve image quality and it is now more properly termed a UW/SP-3000 tomograph. The most modifications have provided the facility with a tomograph with good image quality and very high count rate capabilities. The facility currently supports 14 principal investigators working in Oncology, Cardiology, Neurology, Psychiatry, Radiation Biology, Chemistry, and Physics. With the expansion of the research, the current computer system, a Data General MV18000 with three disk drives, does not have the time available to support the image reconstruction requirements of the users. Typically, for every day the tomograph is used an additional two days of computer time is needed to reconstruct the requested images. The result has been a limit on the number of image planes that can be used (to reduce the amount of data to be reconstructed) and a severe limitation on the number of studies that can be performed. In addition, the disk drives on the MV18000 are older technology and can not support the needed data rates for acquisition of all image planes. The new equipment will resolve these problems by: 1) adding high speed disk drives to the MV18000 to provide the needed speed and capacity; and 2) add a Data General Aviion system for image reconstruction. The Aviion system for image reconstruction. The Aviion system is based on two Motorola 88000 RISC processors and provides a factor of 10 increase in computer speed over the MV18000 for the primary image reconstruction tasks. Taking advantage of the software tool and high speed fiber optic network form Data General, we will be able to tightly couple the MV18000 and the Aviion system to provide the user with image reconstruction times on the order of 30 seconds per image as well as image reconstruction of one study while a new study is being acquired. In addition to the fast reconstruction, the current restrictions on the number of image planes being used will be removed. The result will be a major increase in the productivity of the facility and our users.